The Role of the Transdiaphragmatic Pressure Gradient (TGP) in the Pathophysiology of Proximal Reflux.

Introduction An increased transdiaphragmatic pressure gradient (TGP) is a main element for distal gastroesophageal reflux disease (GERD). The role of TGP for proximal reflux is still unclear. This study aims to evaluate the presence, severity, and importance of proximal reflux in relationship to the TGP, comparing healthy volunteers, obese individuals, and patients with chronic obstructive pulmonary disease (COPD). Methods We studied 114 individuals comprising 19 healthy lean volunteers, 47 obese individuals (mean body mass index 45 ± 7 kg/m2), and 48 patients with COPD. All patients underwent high-resolution manometry and dual-channel esophageal pH monitoring. Esophageal motility, thoracic pressure (TP), abdominal pressure (AP), TGP, DeMeester score, and % of proximal acid exposure time (pAET) were recorded. Results Pathologic distal GERD was found in 0, 44, and 57% of the volunteers, obese, and COPD groups, respectively. pAET was similar among groups, only higher for obese individuals GERD + as compared to obese individuals GERD - and COPD GERD -. pAET did not correlate with any parameter in healthy individuals, but it correlated with AP in the obese, TP in the COPD individuals, and TGP and DeMeester score in both groups. When all individuals were analyzed as a total, pAET correlated with AP, TGP, and DeMeester score. DeMeester score was the only independent variable that correlated with pAET. Conclusions Our results show that (a) TGP is an important mechanism associated with distal esophageal acid exposure and this fact is linked with proximal acid exposure and (b) obesity and COPD both seem to be primary causes for GERD but not directly for proximal reflux.